DNA markers linked to eastern filbert blight resistance in Ratoli hazelnut (Corylus avellana L.)

Eastern filbert blight (EFB), caused by the pyrenomycete Anisogramma anomala (Peck) E. Muller, is a major disease problem and production constraint in orchards of European hazelnut (Corylus avellana L.) in Oregon's Willamette Valley. Host genetic resistance is viewed as the most economical means of controlling this disease. A dominant resistance gene from Gasaway has been used extensively in the hazelnut breeding program at Oregon State University, but concern about the durability of a single resistance gene stimulated a search for new sources of resistance. Ratoli, a minor cultivar from Spain, showed no signs or symptoms of the fungus following a series of inoculations. The objective of this study was to study segregation for disease response in two progenies from crosses of Ratoli with susceptible selections and identify linked DNA markers. About half of the seedlings were resistant, suggesting control by a dominant allele at a single locus. A total of 900 random amplified polymorphic DNA (RAPD) primers and 64 amplified fragment length polymorphism (AFLP) primer combinations were screened. Four RAPD markers and two ALFP markers were identified and a linkage map constructed. On this map, disease resistance was flanked by AFLP marker C4-255 and RAPD marker G17-800 at distances of 0.4 cM and 2.8 cM, respectively. Based on co-segregation with SSR markers, Ratoli resistance was assigned to linkage group 7 while Gasaway resistance is on linkage group 6. Ratoli provides a novel source of EFB resistance, and robust RAPD marker G17-800 is useful for marker-assisted selection.